DK Tank : No experience
Warrior Tank : No experience
Ele Shaman: Absolutely the easiest dps to box. Macros for ele shamans are about the closest you can get if you were doing it manually. Your AoE is really easy too because it is all targeted (the only thing that puts them above mages imo)
Hunter ( which spec? ) : Survival is probably the easiest to box. I believe a few people do have success with the other specs.
Moonkin: While Moonkins are awesome, they have the hardest rotation to macro. You may end up having to give up the sunfire talent in order to get a macro to work, and that is an immediate loss of dps.
Warlock: I currently have my lock specced affliction, and I was surprised how well he did. Some people do demo as well.
Mage: Faceroll.
Holy Priest: Awesome healing. There are quite a bit of spells to manage however, but they are super powerful healers.
Resto Shaman: Resto shamans are great healers too. My 3 healers are 2 holy priest, 1 resto shaman.
Resto Druid: No experience